Index: device/base/device_util_mac.cc |
diff --git a/device/base/device_util_mac.cc b/device/base/device_util_mac.cc |
new file mode 100644 |
index 0000000000000000000000000000000000000000..06604b7c8e16f5d5d2f91c360b91d367e97defc0 |
--- /dev/null |
+++ b/device/base/device_util_mac.cc |
@@ -0,0 +1,32 @@ |
+// Copyright 2016 The Chromium Authors. All rights reserved. |
+// Use of this source code is governed by a BSD-style license that can be |
+// found in the LICENSE file. |
+ |
+#include "device/base/device_util_mac.h" |
+ |
+#include <math.h> |
+ |
+namespace device { |
+ |
+double LMUvalueToLux(uint64_t raw_value) { |
+ // Conversion formula from regression. |
+ // https://bugzilla.mozilla.org/show_bug.cgi?id=793728 |
+ // Let x = raw_value, then |
+ // lux = -2.978303814*(10^-27)*x^4 + 2.635687683*(10^-19)*x^3 - |
+ // 3.459747434*(10^-12)*x^2 + 3.905829689*(10^-5)*x - 0.1932594532 |
+ |
+ static const long double k4 = pow(10.L, -7); |
+ static const long double k3 = pow(10.L, -4); |
+ static const long double k2 = pow(10.L, -2); |
+ static const long double k1 = pow(10.L, 5); |
+ long double scaled_value = raw_value / k1; |
+ |
+ long double lux_value = |
+ (-3 * k4 * pow(scaled_value, 4)) + (2.6 * k3 * pow(scaled_value, 3)) + |
+ (-3.4 * k2 * pow(scaled_value, 2)) + (3.9 * scaled_value) - 0.19; |
+ |
+ double lux = ceil(static_cast<double>(lux_value)); |
+ return lux > 0 ? lux : 0; |
+} |
+ |
+} // namespace device |